P. de Simone

The triple-GEM detector for the M1R1 muon station at LHCb

Twenty-four triple-GEM detectors with 20times24 cm2 active area will equip the inner region of the first station of the muon detector at the LHCb experiment. After three years of R&D to prove that this detector, operated with a CF4 based gas mixture, satisfies the stringent requirements in terms of time performance and radiation hardness, the project is entering in the construction phase. The final design of the detector, the selected materials and the construction procedure and tools will be described in details. The quality control of components, such as planarity measurements on the PCB-panels and the HV test of the GEM foil, as well as the leak test and the X-ray tomography of constructed chambers will be discussed. The chamber equipped with front end electronics, Faraday cage and HV divider is finally tested with cosmics. The construction of the detector, shared between the two production sites of Cagliari-INFN and Laboratori Nazionali di Frascati-INFN, should be completed in spring 2006. The installation is foreseen by the end of the 2006

The LHCb triple-GEM detector for the inner region of the first station of the muon system: construction and module-0 performance

A triple-gas electron multiplier (GEM) detector, operated with the gas mixture Ar/CO2/CF4 (45/15/40), is going to equip station M1, region R1 of the LHCb muon system. A Module-0 of this detector, with full area (20 cmtimes24 cm) GEM foils, was recently built and tested. In this paper, new measurements of efficiency and pad multiplicity are presented. These new measurements were very important to select of the final pad board configuration. The sensitivity to discharges is a very important issue in this type of detector; we discuss here new measurements of the maximum number of discharges that a triple-GEM detector can stand before breakdown, and we show that detector operation in LHCb is safe from this point of view. We also discuss new measurements of the time performance of the detector in the presence of background radiation, indicating that no significant deterioration of the performances is expected in the LHCb environment

A fast multi-GEM based detector for high-rate charged-particle triggering

In this paper, results of a time performance study of gas electron multiplier (GEM)-based detectors are discussed. This study was driven by an R&D activity on detectors for the Level 0 LHCb muon trigger. Results presented in this paper are of more general interest, i.e., for experiments in which high-rate charged-particle triggering is needed. Little interest was given so far to time performance of GEM-based detectors, with the exception of one paper reporting the measurement of a double-GEM detector time resolution with an Ar/CO/sub 2/ (70/30) gas mixture where the authors quoted a time resolution such that high-efficiency muon triggering at LHCb would be impossible. The results reported here, obtained with the addition of CF/sub 4/ and isobutane to the Ar/CO/sub 2/ standard mixture, considerably improve the time performance discussed in the above-mentioned paper, allowing one to reach a time distribution root mean square of 5 ns with an isobutane-based mixture. In these conditions, a spark probability per incoming hadron has been preliminary measured to be in the range 5/spl middot/10/sup -12//spl divide/10/sup -11/ at 95% confidence level. These facts make the triple-GEM detector a promising option for high-rate charged-particle triggering.

Measurement of GEM parameters with X-rays

The gas electron multiplier (GEM)-based detectors have been widely developed in past years and have been proposed for many different applications. In this paper, we report on a method able to provide information on the characteristic parameters of a GEM. A single-GEM detector is illuminated with a high-intensity flux of low energy (5.9 keV) photons and all the electrode currents are measured simultaneously. From the analysis of these measurements we extracted a phenomenological and analytical model able to describe the currents induced on the electrodes as a function of electric fields and GEM voltages when the detector is exposed to a continuous ionizing radiation. This model provides information on the characteristic GEM parameters. In conclusion we briefly describe other methods able to extract in a more direct way GEM parameters.

Advances in fast multi-GEM-based detector operation for high-rate charged-particle triggering

In this paper we summarize the results obtained in an R&D work performed in the period 2000-2003 within the LHCb Collaboration to develop a triple-GEM based detector for the inner region of the first muon station. Since the information coming from this detector will he used at the L0 trigger level, many studies were performed in order to optimize its time resolution. By using CF/sub 4/-based gas-mixtures a time resolution of 4.5 ns RMS was obtained, which translates in efficiencies higher than 96 % in a 20 ns time window for a large operating region. Moreover, measurements of discharge probability per incident charged particle with a high intensity pion/proton beam for these gas mixture are also reported. All these results show that triple-GEM detectors can he used for triggering in the LHCb Muon Detector. Preliminary results on a global aging test performed with a 25 kCi /sup 60/Co source are also reported and compared to other aging tests performed with X-rays and hadron beams.

Advances on micro-RWELL gaseous detector

The R&D on the micro-Resistive-WELL (u-RWELL) detector technology aims in developing a new scalable, compact, spark-protected, single amplification stage Micro-Pattern Gas Detectors (MPGD) for large area HEP applications as tracking and calorimeter device as well as for industrial and medical applications as X-ray and neutron imaging gas pixel detector. The novel micro-structure, exploiting several solutions and improvements achieved in the last years for MPGDs, in particular for GEMs and Micromegas, is an extremely simple detector allowing an easy engineering with consequent technological transfer toward the photolithography industry. Large area detectors (up 1 x 2 m^2) can be realized splicing u-RWELL_PCB tiles of smaller size (about 0.5 x 1 m^2 - typical PCB industrial size). The detector, composed by few basic elements such as the readout-PCB embedded with the amplification stage (through the resistive layer) and the cathode defining the gas drift-conversion gap has been largely characterized on test bench with X-ray and with beam test.

Advances in triple-GEM detector operation for high-rate particle triggering

We report the results of a systematic study of the time performance of triple-GEM detectors operated with several gas mixtures which are new for this kind of detectors. This study was performed in the framework of an R&D activity on detectors for the level 0 LHCb muon trigger. We show that a considerable improvement, with respect to the traditional gas mixture Ar/CO/sub 2/(70/30), is obtained with the fast and high yield based CF/sub 4/ and iso-C/sub 4/H/sub 10/ gas mixtures; time resolutions better than 5 ns. Discharges studies have been performed with high intensity pion/proton beams at the /spl pi/M1 beam facility of the Paul Sherrer Institute (PSI). The results show that the operation of the detector is very stable, if a small fraction of iSO-C/sub 4/H/sub 10/ or a large amount of CF/sub 4/, is used. The role of the electron diffusion in the formation of discharges, has been studied testing two different detector gap geometries.